View source for Publication bias

==Frequency of occurrence==
===Randomized controlled trials===
Publication bias, or bias in interpretation of studies, may occur in 25%<ref>{{Cite journal | doi = 10.1371/journal.pmed.1001189 | volume = 9
| issue = 3 | pages = e1001189 | last = Turner | first = Erick H. | coauthors = Daniel Knoepflmacher, Lee Shapley | title = Publication Bias in Antipsychotic Trials: An Analysis of Efficacy Comparing the Published Literature to the US Food and Drug Administration Database | journal = PLoS Med
| accessdate = 2012-03-21 | date = 2012-03-20 | url = http://dx.doi.org/10.1371/journal.pmed.1001189 }}</ref> to 60% of some types of articles.<ref name="pmid20940209">{{cite journal| author=Eyding D, Lelgemann M, Grouven U, Härter M, Kromp M, Kaiser T et al.| title=Reboxetine for acute treatment of major depression: systematic review and meta-analysis of published and unpublished placebo and selective serotonin reuptake inhibitor controlled trials. | journal=BMJ | year= 2010 | volume= 341 | issue=  | pages= c4737 | pmid=20940209 | doi=10.1136/bmj.c4737 | pmc= | url= }} </ref><ref name="pmid15967761">{{cite journal| author=Decullier E, Lhéritier V, Chapuis F| title=Fate of biomedical research protocols and publication bias in France: retrospective cohort study. | journal=BMJ | year= 2005 | volume= 331 | issue= 7507 | pages= 19 | pmid=15967761 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=clinical.uthscsa.edu/cite&retmode=ref&cmd=prlinks&id=15967761 | doi=10.1136/bmj.38488.385995.8F | pmc=PMC558532 }} </ref><ref  name="pmid15451835">{{cite journal|  author=Chan AW, Krleza-Jerić K, Schmid I, Altman DG| title=Outcome  reporting bias in randomized trials funded by the Canadian Institutes of  Health Research. | journal=CMAJ | year= 2004 | volume= 171 | issue= 7 |  pages= 735-40 | pmid=15451835 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=15451835  | doi=10.1503/cmaj.1041086 | pmc=PMC517858 }}</ref> Publication bias may be associated with the language the study is published in and may be more common in certain areas of study. In the field of complementary and [[alternative medicine]] (CAM), publication bias may be more likely to occur in studies published in languages other than English.<ref name="pmid16086467">{{cite journal |author=Pham B, Klassen TP, Lawson ML, Moher D |title=Language of publication restrictions in systematic reviews gave different results depending on whether the intervention was conventional or complementary |journal=J Clin Epidemiol |volume=58 |issue=8 |pages=769–76 |year=2005 |pmid=16086467 |doi= |issn=
}}</ref>

A possible reason is that typical CAM studies are smaller than trials of conventional medicine.<ref name="pmid16086467"/> According to two European analyses, both including German authors and one from the German [[Cochrane Collaboration|Cochrane]] Center, this bias may be especially prevalent in German publications.<ref name="pmid16824217">{{cite journal |author=Galandi D, Schwarzer G, Antes G |title=The demise of the randomised controlled trial: bibliometric study of the German-language health care literature, 1948 to 2004 |journal=BMC Med Res Methodol |volume=6 |issue= |pages=30 |year=2006 |pmid=16824217 |doi=10.1186/1471-2288-6-30 |issn=}}</ref><ref name="pmid9251637">Lancet. 1997. Language bias in randomised controlled trials published in English and German. http://pubmed.gov/16086467</ref>

Negative studies are less likely to be published<ref name="pmid17443628">{{cite journal| author=Scherer RW, Langenberg P, von Elm E| title=Full publication of results initially presented in abstracts. | journal=Cochrane Database Syst Rev | year= 2007 | volume=  | issue= 2 | pages= MR000005 | pmid=17443628 
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=17443628 | doi=10.1002/14651858.MR000005.pub3 }}</ref><ref name="pmid8015133">{{cite journal| author=Scherer RW, Dickersin K, Langenberg P| title=Full publication of results initially presented in abstracts. A meta-analysis. | journal=JAMA | year= 1994 | volume= 272 | issue= 2 | pages= 158-62 | pmid=8015133 
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=8015133 }}</ref> and have more delays in their publication<ref name="pmid17443632">{{cite journal| author=Hopewell S, Clarke M, Stewart L, Tierney J| title=Time to publication for results of clinical trials. | journal=Cochrane Database Syst Rev | year= 2007 | volume=  | issue= 2 | pages= MR000011 | pmid=17443632 
| url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=17443632 | doi=10.1002/14651858.MR000011.pub2 }}</ref>.

===Studies of diagnostic tests===
Publication bias may occur in studies of [[diagnostic test]]s.<ref name="pmid8610949">{{cite journal |author=Owens DK, Holodniy M, Garber AM, ''et al'' |title=Polymerase chain reaction for the diagnosis of HIV infection in adults. A meta-analysis with recommendations for clinical practice and study design |journal=Ann. Intern. Med. |volume=124 |issue=9 |pages=803–15 |year=1996 |month=May |pmid=8610949 |doi= |url=http://www.annals.org/cgi/pmidlookup?view=long&pmid=8610949 |issn=}}</ref> Publication bias may be more of a problem in diagnostic test research than in randomized controlled trials because studies of diagnostic tests can be secondary analyses of databases and do not have to be registered prior to publication.<ref name="pmid7853038">{{cite journal |author=Irwig L, Macaskill P, Glasziou P, Fahey M |title=Meta-analytic methods for diagnostic test accuracy |journal=J Clin Epidemiol |volume=48 |issue=1 |pages=119–30; discussion 131–2 |year=1995 |month=January |pmid=7853038 |doi= |url=http://linkinghub.elsevier.com/retrieve/pii/0895-4356(94)00099-C |issn=}}</ref>